The invention relates to a process for the production of a container provided with a container opening, having a substantially rigid outer container and an inner bag disposed therein which is in contact with the later container contents, these respectively comprising different thermoplastic plastics which are not bonded to each other, and a pressure equalisation opening, disposed in the outer container, which equalises a pressure difference between the outer container and the inner bag, wherein a preliminary moulding, comprising two coaxial tubes which have a sufficient length for manufacture of the container, is first produced by co-extrusion between the opened halves of the blow mould, the blow mould is closed and with that an outwardly-projecting base seam is formed, the excess material in the base area of the container that is to be manufactured being squashed out in such a way that the material of the outer container which is in contact in the area of the seam is welded together, the tube which forms the inner bag is clamped, axially fixed and welded between the wall sections of the outer container and the inner bag is subjected to pressure so that the walls of the preliminary moulding lie against the contours of the blow mould from inside.
Furthermore, the invention relates to a container, preferably produced according to the process, with a container opening, substantially comprising a rigid outer container and an inner bag disposed therein, which is in contact with the later container contents.
A process of the type considered here is disclosed in WO 99/11451. The characterising feature of this process is that the pressure equalisation opening, via which the pressure difference existing between the outer container and the inner bag is equalised, is preferably configured as a lenticular or ellipsoid hole in the outer container, wherein this hole comes into being after completion of the actual forming process by cutting away a wall section of the outer container with the help of a cutting tool.
This means that the outer wall, against which the very thin flexible inner bag lies, must be completely cut away in at least one very small area without causing any damage to the inner bag. Processing of the outer container implies an indispensable contact between the cutting tool and the inner bag. The substantially most important quality features of the process and of the container manufactured according to the process cannot be realised simultaneously to an equal degree. They diverge in the present process, or container. On the one hand it must be possible to effect pressure equalisation between the outer container and the inner bag, which is necessary due to the volume reduction in the inner bag associated with the dispensing of the container contents. On the other hand, the container must be completely sealed, i.e. damage to the inner bag must be avoided at all costs, otherwise the container would be unusable. The difficulty of fulfilling both tasks satisfactorily is discussed in WO 99/11451. For example, it is stated that due to the wall strength tolerances of the outer container which occur as a result of its fabrication, wherein the wall thickness can vary between 1 and 1.5 mm, in price the depth of cut must be set so that it is guaranteed that a hole which actually penetrates the outer container results from the cutting process. Damage to the inner bag cannot be ruled out in every case. For this reason, preferred process steps and tools which are to be used in order to minimise the danger of damage to the inner bag are described in WO 99/11451.
A further disadvantage of the disclosed process is that the configuration of the pressure equalisation opening does not take place immediately after the forming process. The process step of cutting cannot take place on the plastic blowing machine, and especially not when the blowing mould is closed. The additional processing machine, or its tools, which are required for the suggested cutting process and the working steps which have been made necessary lead to an increase in costs and a reduction in productivity.
Furthermore, it can be desirable to connect a pump or an atomiser to the container opening of the container of the considered type, via which the material in the inner bag of the container is charged or removed. Depending on the configuration of the utilised pump or atomiser, the pressure equalisation opening can be partially or completely closed by the suitable pump or atomiser. In other words, it is not possible to attach any adaptor to the container in question, rather the particular position of the pressure equalisation opening of the respective embodiment example must be taken into consideration. Especially unfavourable positions for the wall opening are, in this case, positions in the shoulder area and in the area of the container jacket surface. The most suitable position for the wall opening, the container base, is expressly not mentioned.